The present invention relates generally to pressure monitoring systems of the purge gas type in which purge gas is injected into media to facilitate measurement of media pressure. In such systems, a piezometer tube runs from a pressure measuring instrument into a medium to be monitored, and pressurized gas is passed along the tube to escape as bubbles at the end of the tube submerged in the monitored medium. The pressure of the gas escaping from the tube is a function of the pressure of the medium into which it is bubbled, and this pressure is monitored via a remote instrument such as a pressure transducer or balance beam manometer to provide an indication of variations in the depth, density, or other parameters of the medium. The invention is particularly concerned with a temperature compensating apparatus for a purge gas pressure monitoring system.
Purge gas pressure monitoring systems are used in various applications, including monitoring of water depth in rivers, reservoirs and other large bodies of water (commonly known as hydrologic water stage monitoring), monitoring of fluidized bed pressures, pressure monitoring of gases, liquids, and mixtures of liquids and gases, density monitoring, and so on. One error which typically arises in such systems is a result of temperature variations along the piezometer line.